Manual of Monsters is a source book for Warcraft The Roleplaying Game and was published in 2003. It contains descriptions and game statistics for a large number of creatures that inhabit the Warcraft setting. As the book was published before the release of World of Warcraft, it only covers a few creatures that were introduced in the MMORPG and mostly covers material from the RTS series.

The book is out of print. However, it can still be obtained in a PDF format. A new creature source book for the World of Warcraft: The Roleplaying Game was released on February 7th, 2007 called Monster Guide. It covers new creatures that appear in World of Warcraft and updates some of the creatures from Manual of Monsters with new game statistics and rules of the new Warcraft RPG game.

Chris Metzen was a co-author and a member of the "Design Assistance and Additional Material" staff for the book.

Finally, Appendix Three contains original lore for monsters and creatures adapted into the Warcraft Setting from other d20 books (Monster Manual v3.5, Creature Collection Revised, Creature Collection II: Dark Menagerie, and Tome of Horrors). According to the book the updated lore takes precedence over descriptions found in the previous non-Warcraft books. The section also contains information on how to incorporate other monsters into a campaign for the Warcraft RPG. The background lore could be used by someone who wanted to include the monsters in their campaigns.[1]

"Other Monsters in Azeroth... Some creatures in Manual of Monsters are similar to the described in the MM-centaur, dragons, elementals, golems, and so on. In some cases the MM descriptions are suitable for use as-is, such as for elementals. Under circumstances, the creature receives no listing in the Manual of Monsters. In other cases, monsters are different enough in their ecology or abilities to require a new description here. When a creature is listed in the Manual of Monsters with the same one as the MM, the description in this book takes precedence for a Warcraft campaign. The same is true for an animals or vermin particular to the world of Azeroth, as described in Appendix One. In the case of identical types of animals the ones in the Manual of Monsters takes precedence.[1]

The Appendix Three was split into several sections which sometimes included a small background explanation on how the material related to biology or history of Azeroth. The following is a listing of some of these quotes;

The Kaldorei count many more allies than have been documented so far. Amongst these allies are several species from the Tome of Horrors by Necromancer Games. Some are ancient allies, others newly recruited (or reclaimed) allies, befriended by the night elves in the wake of their lost immortality.[3] The minions of the Burning Legion are countless, yet below is a list of shock troops, animal cohorts, and generals alike.[4] In addition to quilboar, tauren, elves, and orcs, other sapient species populate the world of Azeroth. Three of them are described in the Tome of Horrors.[5] Orcs and goblins are not the only goblinoids on Azeroth. Some of the previously unknown species are crossbreeds, while others seem to be races unto themselves. Three of these species are discussed briefly below.[5] The diversity of animal life on Azeroth is limitless. In addition to the creatures described elsewhere in this book, several species described in the Tome of Horrors can also be found on Kalimdor and throughout Azeroth.[5] In addition to the diversity of life on the surface of Kalimdor, the seas of Azeroth are also teeming with life. Much of this life is mundane, if monstrously large, though the sea has her secrets — and threats. The following aquatic creatures listed in the Tome of Horrors can be found in the rivers, lakes and oceans in around Kalimdor.[5]

Appendix III has some controversy surrounding it by Warcraft fans. Although some material from Appendix III has made it into other sources, this does not necessarily mean that all the material will make it into future sources. Even though some of the material has made it into other sources, it is the opinion of some of the freelance writers and editors of the RPG line, and many of the fans, that Appendix III is not considered canon.

That MoM appendix was full of ideas about how you might incorporate monsters from other sources into the game, if you feel like it. Until I see mites running around in a Warcraft computer game, I wouldn't consider them canon.

Oh, there was a question. I don't think I have the power to make that declaration, since I'm not a Blizzard employee. What I can tell you is that Blizzard signs off (approves) every book before we publish it. So, they look it over, ask us to make any changes (i.e., "tauren don’t know about the Green Dream; can you remove this paragraph?"), then say, "Okay, publish this." I also think that these days we (and by "we" I mean "I") put more effort into making sure Metzen is cool with everything before the material makes it into the final manuscript. Also, sometimes when I ask Blizzard for reference material (i.e., "What can you tell me about Sandfury trolls?"), they quote my own books back at me.

From a marketing perspective, Appendix III could help attract customers of D&D and other d20-type games to the Warcraft franchise if creatures familiar to them were included or available for use during RPG gameplay, or maybe the way around, that Warcraft gamers would get more involved into the D&D franchise.

Blizzard has never officially given their stance on the issue. Since WoWWiki strives to have a neutral point of view on official lore (both canon & non-canon) it is included on Manual of Monsters/Appendix Three and a link in the relevant articles. This information is separated from the other lore so that people can decide themselves if they consider it canon or not.